If I am having a graph of displacement versus time and at time = 0 second, the displacement of an object is 10 metres.

I need to know: what is its initial velocity?

Is it 10 m/s?

(Note that the average velocity is given: 20 m/s)

Also, its a rectilinear motion and has constant (0$m/s^2$ ) acceleration throughout.


closed as off-topic by Kyle Kanos, peterh, heather, Jon Custer, M. Enns Aug 7 '17 at 0:49

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – Kyle Kanos, peterh, heather, Jon Custer, M. Enns
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ The initial velocity may be 0. Graph will start from y axis at point 10m instead of 0. $\endgroup$ – Wrichik Basu Aug 6 '17 at 12:50
  • $\begingroup$ @WrichikBasu Yes, graph starts at y=10m, but why initial velocity may be 0? $\endgroup$ – Ravi Prakash Aug 6 '17 at 12:51
  • 1
    $\begingroup$ See, that was a guess. I believe that your question is unclear, and you need to put up more info on what type of motion you're analysing and similar facts. On your current question, I cannot say more. Others will surely help you, if they can. $\endgroup$ – Wrichik Basu Aug 6 '17 at 12:54
  • $\begingroup$ @WrichikBasu Is the question clear now? Or more info needed?? $\endgroup$ – Ravi Prakash Aug 6 '17 at 12:56
  • $\begingroup$ Is it possible to upload a picture of the graph? $\endgroup$ – Wrichik Basu Aug 6 '17 at 13:05

If the acceleration is $0$ then the velocity does not change and the instantaneous velocity is the average velocity, i.e. $20m/s$. The graph of $x$ as a function of $t$ will be a line with slope $20$, i.e. $x=20 t + x_0$, and going through the point $(x,t)=(10,0)$


As you have stated that it's a rectilinear motion and given acc=0, this implies that

average velocity = instantaneous velocity

because the body neither accelerates nor decelerates.Only when there is a acc/dec there is a change in velocity. So it's initial velocity = average velocity.


Not the answer you're looking for? Browse other questions tagged or ask your own question.